Greenpeace says two of its people have been sentenced to suspended one-year jail terms for stealing a box of whale meat during an investigation.
The pair, dubbed the Tokyo Two, admitted to taking the whale meat, saying it was smuggled off a whaling ship by crewmen and was to be sold on the black market.
But Junichi Sato and Toru Suzuki said they intercepted the meat in an effort to expose official corruption for the public good.
The ABC reports they were backed in court by a whaling industry insider who told of the systemic theft of whale meat by crew and members of the Institute of Cetacean Research, one of the agencies in charge of Japan's scientific whaling programme.
Prosecutors wanted the pair to go to prison for 18 months.
The case has attracted international attention.